hi
140 discs are available but I think only Formula uses them in older models and only for the rear.... so it might just be a huge pita to get them...
Plus you dont really have a choice anyhow.... if the bike has brake bosses than these better be in the IS ( Int Standard) position, where the rotor size is than fixed to the correspondent brake you buy ...

There is the option with some brakes to go bigger rotor size.. with adapters.. that is not necessary..
160 mm is just fine